Excess-pressure means for multicylinder hydraulic systems



April 2 1, 1959 P. BILLEN ET AL EXCESS-PRESSURE MEANS FOR MULTI-CYLINDER HYDRAULIC SYSTEMS 2 Sheets-Sheet 1 Filed Jan. 17, 1955 I HU \NUE

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EXCESS-PRESSURE MEANS FOR MULTI- CYLINDER HYDRAULIC SYSTEMS Peter Billen, Leverkusen-Kuppersteg, and Willi Linnerz, Dusseldorf-Eller, Germany, assignors to Schloemann Aktiengesellschaft, Dusseldorf, Germany Application January 17, 1955, Serial No. 482,363

Claims priority, application Germany February 12, 1954 6 Claims. (Cl. 60-97) Multi-cylinder cable-sheathing presses, for instance two-cylinder presses, have to be capable of being so controlled, either by hand or automatically, that with billets that may possibly be at different temperatures a higher pressure can be exerted on the cooler billet than on the warmer billet. Under some circumstances such great differences in pressure may occur from this cause that the seating of the billet-containers is over-stressed, and damage or deformation is possible as a result. These great difierences of pressure, and the damage incidental thereto, may also occur if a separate pump is allocated to each press cylinder, and then for any reason one pump drops out during the pressing operation. The object of this invention is to protect hydraulic extrusion presses which are provided with two cylinders against such damage as might be caused by excessive differences between the pressures in the two cylinders, without interfering with such normal differences of pressure as may arise for instance owing to a difference in temperature between two billets that are being extruded at the same time.

This invention obviates these disadvantages by means of a pressure-equaliser, in which, upon a predetermined difference of pressure between the pressures prevailing in the working-cylinder spaces being exceeded, an outlet communicating with the pressure space of higher pressure is opened, which puts the pressure spaces of the two working cylinders into communication with one another for the purpose of equalising the pressure therein. As a pressure-equaliser there may for instance be provided a slide-valve gear or a drop-valve gear. Details and advantages of both these constructions are more fully explained in the following description of examples of construction.

The invention is diagrammatically illustrated by way of example in the drawing, in which:

Figure 1 shows in section a two-cylinder cable-sheath ing press with slide-valve gear; and

Figure 2 shows the same press but with an equilising device controlled by drop-valve gear.

In the two-cylinder presses illustrated in Figures 1 and 2, a cable 1 travels perpendicularly to the plane of section through a receiver or container 2, before which billets 3 are located. Rams or pressing stems 4, which push the billets into the receiver 2, are mounted on plungers 5 and 6, which slide in working cylinders 7 and 8. Tension rods 9 take up the forces occurring between the cylinders 7 and 8 and the receiver 2 during the pressing work. The plungers 5 and 6 are acted upon by pressure fluid in cylinder spaces 10 and 11, supplied through pipe lines 12 and 13, by way of a control stand. In Figure 1, one working-cylinder space 10 is in communication by way of a pressure pipe 14 with a pressure space 17 in one pressure casing 27 of an equaliser 25, and the other working-cylinder space 11 is .in communi-- cation by way of a pressure pipe 15 with a pressure space 16 in another pressure casing 26 in the equaliser States Patent 0 25. Between the two pressure casings 26 and 27 there is a slide-valve casing 18. In this slide-valve casing 18 a piston slide valve 19 is provided, which during normal working establishes a fluidtight closure between the pressure spaces 16 and 17. The piston valve 19 has towards each side a pulling and guiding rod 20, each provided with a plate 21. Adjustable compression springs 22 bear against the plates 21.

The method of working is as follows: The two plungers 5 and 6 are actuated by pressure fluid supplied to the working-cylinder spaces 10 and 11 through the pipe lines 12 and 13, so that the rams or pressing stems 4 connected with the plungers 5 and 6 act upon the billets 3 and introduce them into the receiver 2. In a known manner, in the receiver 2, the billet 3 is shaped by a chamber tool, not shown, in such a way that a sheath forms around the cable 1. The working-cylinder spaces 10 and 11 communicate by way of the pipes 14 and 15 with the pressure spaces 16 and 17 of the equaliser, and press upon the surfaces of the piston valve 19. So long as the pressures from both sides are equal the piston valve is not displaced, but is held in a central position by the compression springs 22. Thus the pressure spaces 16 and 17 remain separated from one another by the piston valve 19.

If two billets at different temperatures are being pressed at the same time, the plunger acting upon the cooler billet must exert a greater pressure than the plunger acting upon the hotter billet, in order that the extrusion may proceed uniformly, and the present invention will not interfere with this, unless the difference in pressure and the space 17 and the pressure in the cylinder space 11, the pipe 15 and the space 16 would merely cause the piston valve to move a short distance to the right or the left without opening any communication between the two pressure spaces 16 and 17 and therefore between the two cylinder spaces 10 and 11, Such communication would only be opened it the difference of pressure became great enough to move the piston valve completely out of its own valve casing against the resistance of the spring 22, and the compression of the springs would be so adjusted that this would only occur when the pressure difierence threatened to become dangerous.

If from any cause the pressure in the working-cylinder space 11 becomes for instance more than 20 percent higher than the pressure in the working-cylinder space 10, and the compression springs 22 are so adjusted that with such a diflerence of pressure they permit a complete displacement of the piston valve, then at this pressure the piston valve is dislodged, since the pressure from the working-cylinder space 11 is propagated through the pipe line 15 to the pressure space 16, acts there upon one surface of the piston valve 19, and pushes this completely out of the slide-valve casing 18, overcoming the forces of the left-hand spring 22 and of the counter-pressure upon the other piston surface. The pressure fluid can now flow from the working-cylinder space 11 through the pipe '15 to the pressure space 16, and from there to the pressure I space 17, and then through the pipe line 14 into the 17 again, and the pressure fluid in the cylinder space 10 no longer has any connection with the cylinder space 11.

Patented Apr. 21, 1959 The two plungers 5 and 6 can now be acted upon by fluid independently of one another.

The press illustrated in Figure 2 works in the same manner as the one previously described. The difference lies in the valve-control gear 60, which permits a reliable sealing between the two cylinder spaces even with only slight difierences of pressure.v The working-cylinder spaces 10 and 11 communicate by way of the supply pipes 30 and 31 with cylinder spaces 32 and 33' respectively. In the cylinder spaces 32 and 33 there are plungers 34 and 35, which act upon two equal arms of a three-armed lever 36, which can turn about a stationary fulcrum at 37. The third arm 38 of the three-armed lever can act through plates 47 upon valve rods 47', carrying valve cones 41 and 42. Adjustable springs 48 bearing against the plates 47 keep the valves closed. The inlet pipes 30 and 31 are connected by way of pipes 50 and 49 with valve chambers 46 and 45- respectively, and by way of further pipes 45 and 49 with valve chambers 43 and 44 respectively. These valve chambers 43 and 44 are shut off from the valve chambers 45 and 46 respectively in a fluidtig-ht manner by the valve cones 41 and 42. This device operates in the following manner: If equal pressures prevail in the two working cylinders 10 and 11, the pressure of the fluid is propagated through the inlet pipes 30 and 31 to the cylinder spaces 32 and 33. So long as equally high pressures are present in the two cylinder spaces 32 and 33, neither of the plungers 34 or 35 acting upon the lever 36 can be impelled in the direction outwards from the cylinder spaces, but they counter-balance one another. The lever arm 38 therefore stands midway between the valve-rod plates 47, and does not act upon the valves. The valves are kept closed by the elasticity of the springs 48.. The valve spaces 43 and 45, and likewise the valve spaces 44 and 46, are not in communication, on account of the sealing valve cones 41 and 42. Since the two valve chambers are shut off from one another, there is no possible liquid connection between the two working-cylinder spaces 10 and 11. If in the left-hand working-cylinder space 11 a pressure arises which is higher by more than 20 percent, for example than the pressure in the right-hand working-cylinder space 10, the pressure of the space 11 is propagated through the pipe 31 into the cylinder space 33, and the pressure fluid drives the plunger 35 forward. Since on the opposite side, in the cylinder space 32, there is no corresponding counter-pressure, the plunger 34 is driven further into this cylinder through the medium of the lever 36. The arm 38 connected with the lever arms 36 is thereby tilted towards the right, presses upon the righthand valve-rod plate 47, and therefore lifts the valve cone 41 ofi its seat against the pressure of the spring 48. The pressure fluid, which has communication by way of the pipes 31 and 49 with the valve chamber 45, can now flow through the opened valve 41 into the valve chamber 43, and further, by way of the pipe lines 40' and 30, into the right-hand working-cylinder space 10, and can continue to do so until the pressure diiference between the two working-cylinder spaces 10 and 11 falls below 20 percent. When this occurs, the right-hand spring 48 closes the valve 41, and at the same time, through the medium of the lever arms 38 and 36, pushes the plunger 35 into the cylinder 33, the plunger 34, actuated by the the pressure fluid of the working-cylinder space 10 by way of the pipe 30, following the lever 36. From now onwards no pressure fluid can flow over from the working-cylinder space 11 to the right-hand working-cylinder space 10.

When there is complete equalisation of pressure between the two working-cylinder spaces, the lever 38 will be able to readjust itself between the two valve-rod plates 47, since in this case the pressure fluid from the workingcylinder spaces 10 and 11 exerts the same pressure, through the pipes 30 and 31, upon both the plungers 34 and 35, so that the valve-rod plates 47 and the springs 48 are completely relieved. When moderate diflerences of pressure occur, in the normal working of the press, a certain idle movement of theplungers 34 and 35 and of the rod 38 can occur without producing any effect upon the valves 41 and 42.

What is claimed:

1. An excess-pressure protective device for a hydraulic system controlling the operation of two hydraulic motor cylinders, comprising: valve means urged in one direction by the fluid pressure in a pressure space in open communication with one of the cylinders and urged in the opposite direction by the fluid pressure in a pressure space in open communication with the other cylinder, and resilient means resisting movement of the valve means in either direction, the valve means after being moved beyond a predetermined distance in either direction, opening communication between the two cylinders upon the occurrence of a predetermined fluid-pressure build-up in one of the said cylinders.

2. An excess-pressure protective device for a hydraulic system controlling the operation of two hydraulic motor cylinders, comprising: two pressure casings, each en-- closing a pressure space, and each of these pressure. spaces being in communication with one of the cylinders, a slide-valve casing located between the two pressure casings, the interior of the slide-valve casing being in open communication with both the pressure spaces, a piston valve slidable in a fluidtight manner in the slide-valve casing, and thereby normally establishing a fluidtight closure between the two pressure spaces, and adjustable springs tending to maintain the piston valve in, its mid position in the valve casing, the piston valve being operable to be moved, against the resistance of the springs,

by an excessive difierence of pressure between the two pressure spaces, right out of the valve easing into one of the pressure spaces, thereby opening communication between the two pressure spaces, and therefore between the two cylinders.

3. An excess-pressure protective device for a hydraulic system as claimed in claim 2, the two pressure casings and the slide-valve casing being united to form a unitary casing.

4. An excess-pressure protective device for a hydraulic system controlling the operation of two hydraulic motor cylinders, comprising: two plunger cylinders, each in open communication with one of the motor cylinders, two plungers, each slidable in one of the plunger cylinders,

,, a three-armed lever, two arms of which engage the outer ends of the two plungers in such a way that the fluid pressure in the two plunger cylinders tends to turn the lever in opposite directions about its fulcrum, two valve casings, each divided into two compartments, one compartment of each valve casing being in open communication with one of the motor cylinders and the other compartment with the other motor cylinder, a valve in each Valve casing capable of establishing and interrupting communication between the two compartments of the valve casing, and

spring means tending to keep the valves closed, the third arm of the three-armed lever being connected to push one or other of the valves open whenever the diflference in pressure between the two plunger cylinders, and therefore between the two motor cylinders, becomes excessive.

5. An excess-pressure protective device for a hydraulic system controlling the operation of two hydraulic motor of liquid under pressure to the motor cylinders, and to be maintained in a mid position when the two pressures are equal to one another, and to be moved in one direction or the other by the greater pressure when they are unequal, and valve means normally closing communication between the two pressure chambers, the said movable means being operable to open the said valve means,

after a predetermined amount of 10st motion, by which the volume of one pressure chamber has been increased and that of the other has been diminished, when the pressure in one of the pressure chambers, and therefore in the motor cylinder communicating therewith, greatly exceeds the pressure in the other pressure chamber and the other motor cylinder.

6. An excess-pressure protective device for a hydraulic system controlling the operation of two co-axial hydraulic motor cylinders acting in opposite directions, comprising: two pressure chambers, each in open communication with one of the motor cylinders, movable means acted upon by the pressure occasioned in both the pressure chambers by the delivery of liquid under pressure thereto and maintained in a mid position when the two pressures are equal to one another but moved in one direction or the other by the greater pressure when they are unequal, and valve means normally closing communication between the two pressure chambers, the said movable means operating to open the said valve means after a predetermined amount of lost motion, by which the volume of one pressure space is increased and that of the other is diminished, when the pressure in one of the preessure chambers, and therefore in the motor cylinder communicating therewith, greatly exceeds the pressure in the other pressure chamber and in the other motor cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 907,077 Mereta Dec. 15, 1908 2,153,637 Niven et a1 Apr. 11, 1939 2,270,943 Freundel et al. Jan. 27, 1942 2,572,749 Noordeman Oct. 23, 1951 2,616,259 Quintilian Nov. 4, 1952 2,636,350 Alcorn Apr. 28, 1953 FOREIGN PATENTS 698,344 Great Britain Oct. 14, 1953 

